Providing acknowledgement information by a wireless device

ABSTRACT

In general, to provide acknowledgment information by a first wireless device, the first wireless device sends repeated instances of acknowledgment information in respective first and second frame structures, in response to receipt of first information from a second wireless devalue. In addition, the first wireless device also sends further acknowledgment information in the second frame structure that is responsive to second information received from the second wireless device.

BACKGROUND

Various wireless access technologies have been proposed or implemented to enable mobile stations to perform communications with other mobile stations or with wired terminals coupled to wired networks. Examples of wireless access technologies include GSM (Global System for Mobile communications) and UMTS (Universal Mobile Telecommunications System) technologies, defined by the Third Generation Partnership Project (3GPP); and CDMA 2000 (Code Division Multiple Access 2000) technologies, defined by 3GPP2.

As part of the continuing evolution of wireless access technologies to improve spectral efficiency, to improve services, to lower costs, and so forth, new standards have been proposed. One such new standard is the Long Term Evolution (LTE) (also referred to as the Evolved Universal Terrestrial Radio Access (EUTRA) standard) from 3GPP, which seeks to enhance the UMTS technology.

In a wireless communications network, information is communicated wirelessly between mobile stations and base stations. In response to information received in the downlink (from base station to a mobile station), the mobile station can send acknowledgment information to either provide a positive acknowledge (ACK) of successful receipt of the data, or negative acknowledgment (NAK) to indicate that the data was not successfully received. To improve reliability, a recent development of LTE proposed use of ACK/NAK repetition, in which a mobile station repeats the sending of an ACK or NAK in response to downlink information from the base station, to improve the likelihood that the base station receives the ACK or NAK. This may be particularly useful when the mobile station is in a region of a cell or cell sector that has relatively poor wireless conditions, such as at the edge of the cell or cell sector, or in another location associated with obstructions that may result in reduced signal strength or increased noise.

An issue associated with repetition of ACK/NAK is that in response to consecutively received pieces of downlink information, the acknowledgment information for such consecutively received pieces of information may collide, which may cause the base station to not reliably receive the acknowledgment information associated with the consecutively transmitted pieces of downlink information.

SUMMARY

In general, according to a preferred embodiment, a method of providing acknowledgment information by a first wireless device comprises the first wireless device sending repeated instances of acknowledgment information in respective first and second frame structures, in response to receipt of first information from a second wireless device. In addition, the first wireless device also sends further acknowledgment information in the second frame structure that is responsive to second information received from the second wireless device.

Other or alternative features will become apparent from the following description, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are described with respect to the following figures:

FIG. 1 is a block diagram of an example arrangement that includes a wireless communications network that incorporates some preferred embodiments of the invention;

FIGS. 2 and 3 illustrate the sending of downlink data and responsive repeated instances of acknowledgment information in accordance with some preferred embodiments; and

FIG. 4 is a flow diagram of a process of sending acknowledgment information, according to an embodiment.

DETAILED DESCRIPTION

In accordance with some preferred embodiments, a technique or mechanism is provided to allow for transmission of repeated instances of acknowledgment information while avoiding the issue of collisions in acknowledgment information sent in response to multiple pieces of received information. In some embodiments, the acknowledgment information is sent by a mobile station in the uplink (from the mobile station to the base station) in response to receipt of downlink data from the base station. The acknowledgment information includes either a positive acknowledgment (ACK) to indicate successful receipt of the data, or a negative acknowledgment (NAK) to indicate unsuccessful receipt of the data.

To improve reliability under certain conditions, the mobile station can be configured to perform ACK/NAK repetition, in which multiple instances of the ACK/NAK information is sent in response to receipt of a particular piece of downlink data. In some implementations, the number of ACK/NAK repetitions configured in the mobile station can be two. In other implementations, the mobile station can be configured to send three or four or more instances of the ACK/NAK information (number of ACK/NAK repetitions is three or four or more). ACK/NAK repetition is useful when the mobile station is located in a region of a cell or cell sector that is associated with unreliable wireless signaling. For example, the mobile station may be located at the edge of the cell or cell sector, or the mobile station may be located in a region with obstructions that reduce signal strength or increase noise.

An issue associated with performing ACK/NAK repetition is the likelihood of collisions of ACK/NAK information when the mobile station sends respective repeated ACK/NAKs in response to consecutively received pieces of downlink data. In accordance with some embodiments, to eliminate or reduce the likelihood of collisions of ACK/NAK information, the repeated instance of an ACK/NAK may be communicated in a format that allows for multiple ACK/NAKs (that are responsive to different pieces of downlink data) to be transmitted together. Thus, this predefined format allows for the repeated ACK/NAK responsive to a first piece of data to be sent by the mobile station together with the first ACK/NAK responsive to a second piece of downlink data.

In some embodiments, the wireless communications network is according to the Long Term Evolution (LTE) standard from 3GPP (Third Generation Partnership Project), which is an enhancement of the UMTS (Universal Mobile Telecommunications System) wireless technology. The LTE standard is also referred to as the EUTRA (Evolved Universal Terrestrial Radio Access) standard. Reference to an LTE (or EUTRA) wireless communications network refers to the wireless communications network that conforms to the requirements of the LTE (or EUTRA) standard developed by 3GPP, as that standard currently exists or as the standard evolves over time. Note that LTE (or EUTRA) can refer to the current LTE (or EUTRA) standard, or to modifications of the LTE (or EUTRA) standard that are made over time. It is expected that in the future a standard that has evolved from LTE (or EUTRA) may be referred to by another name. It is contemplated that the term “LTE” or “EUTRA” as used herein is intended to cover such future standards as well. In alternative embodiments, wireless communications networks according to other standards can be employed.

Although reference has been made to transmitting repeated uplink ACK/NAKs in response to downlink data, it is noted that other preferred embodiments of the invention can be applied to scenarios in which a base station transmits a downlink ACK/NAKs in response to uplink data from the mobile station. Moreover, although reference is made to sending ACK/NAK in response to received data, it is noted that ACK/NAK can also be sent in response to control signaling.

FIG. 1 shows an example wireless network in which some embodiments of the invention can be provided. The wireless network includes a base station 100 that includes an antenna array or other antenna assembly 102 for sending wireless signals into a cell sector 108. A cell sector is one section of a cell of a cellular network. In alternative implementations, element 108 can represent an entire cell. More generally, a “cell segment” refers to either a cell or a cell sector.

Although just one base station is depicted in FIG. 1, it is noted that a wireless network would typically include multiple base stations. In some embodiments, the wireless network is an LTE wireless network.

In an LTE wireless network, the base station 100 is an enhanced node B (“eNode B”), which includes a base transceiver station that includes the antenna array 102. The base station 100 may also include a radio network controller that cooperates with the enhanced node B. The radio network controller and/or enhanced node B can perform one or more of the following tasks: radio resource management, mobility management for managing mobility of mobile stations, routing of traffic, and so forth. Note that one radio network controller can access multiple eNode Bs, or alternatively, an eNode B can be accessed by more than one radio access controller.

More generally, the term “base station” can refer to a cellular network base station, an access point used in any type of wireless network, or any type of wireless transmitter to communicate with mobile stations.

As depicted in FIG. 1, the base station 100 includes one or more central processing units (CPUs) 122, which is (are) connected to storage 124. Moreover, the base station 100 includes software 126 that is executable on the CPU(s) 122 to perform tasks of the base station 100.

The mobile station 110 of FIG. 1 also includes one or more CPUs 130 that are connected to storage 132. The mobile station 110 also includes software 134 that is executable on the CPU(s) 130 to perform tasks of the mobile station 110. In addition, the mobile station 110 includes an interface 131 to communicate wirelessly with the base station 100.

The base station 100 is connected to a serving and/or packet data network (PDN) gateway 112, which terminates the user plane interface toward the enhanced node B and assumes the responsibility for packet routing and transfer towards an external network 114, which can be a packet data network such as the Internet or other types of network.

The arrangement depicted in FIG. 1 is provided for purposes of example. In other implementations, other wireless network arrangements are used.

In accordance with some embodiments, downlink data in an LTE wireless communications network is transmitted in PDSCH (physical downlink shared channel) subframes. The PDSCH is a traffic channel. In other implementations, the downlink data can be transmitted in other downlink traffic channels. An LTE subframe is a portion of an LTE frame. An LTE frame has a predefined overall time length that is divided into a predefined number of time slots. An LTE frame is made up of multiple subframes, where an LTE subframe can include some predefined number of the slots (e.g., two slots) of the LTE frame.

In response to receiving downlink data in a PDSCH subframe, the mobile station transmits acknowledgment information (ACK/NAK) to indicate successful or unsuccessful receipt of the downlink data in the PDSCH subframe. In some embodiments, the ACK/NAK is sent by the mobile station in the uplink direction in a PUCCH (physical uplink control channel) subframe. More generally, the repeated instances of ACK/NAK are sent in consecutive frame structures, where a “frame structure” can include a subframe or some other frame structure.

As noted above, ACK/NAK repetition can be enabled for at least one mobile station that the base station 100 is communicating with. If the mobile station is configured to perform ACK/NAK repetition by sending two repeated instances of the ACK/NAK, then the mobile station will respond to a downlink PDSCH subframe by sending two repeated instances of ACK/NAK in consecutive PUCCH subframes. For example, as shown in FIG. 2, in response to downlink data_1 received in PDSCH subframe n, a mobile station configured to perform ACK/NAK repetition will send two instances of ACK/NAK (each instance represented as ACK/NAK_1) in consecutive PUCCH subframes n+4 and n+5.

FIG. 2 also indicates that another piece of downlink data (data_2) is scheduled to be transmitted to the same mobile station in the next consecutive PDSCH subframe (n+1). Since the mobile station is configured to perform ACK/NAK repetition, the mobile station will send two repeated instances of ACK/NAK_2 in consecutive PUCCH subframes (n30 5, n+6).

Note that in this example, one instance of ACK/NAK_1 and one instance of ACK/NAK_2 are scheduled to be transmitted in the same PUCCH subframe (n+5). If not properly handled, ACK/NAK_1 will collide with ACK/NAK_2 in PUCCH subframe n+5.

To address this issue, in accordance with some embodiments, ACK/NAK_1 and ACK/NAK_2 are transmitted together in PUCCH subframe n+5 using a predefined format that allows for communication of multiple different pieces of ACK/NAK information. In some embodiments, an ACK/NAK is communicated as a single bit, where the bit having a first value (e.g., “1”) represents ACK, and the bit having a second value (e.g., “0”) represents NAK. In such embodiments, sending two pieces of ACK/NAK information refers to sending two information bits in the PUCCH subframe (e.g., ACK/NAK_1 is sent in a first bit, while ACK/NAK_2 is sent in a second bit).

In one example implementation, the predefined format that allows for transmission of multiple different ACK/NAK bits in the same PUCCH subframe is referred to as format 1b. Format 1b differs from a different PUCCH format 1a, in which only a single ACK/NAK bit is allowed in the PUCCH subframe. In the example of FIG. 2, ACK/NAK_1 sent in PUCCH subframe n+4 is according to format 1a, and ACK/NAK_2 in PUCCH subframe n+6 is also according to format 1a. However, ACK/NAK_1 and ACK/NAK_2 in PUCCH subframe n+5 are sent together according to format 1b. In one implementation, the two ACK/NAK bits are transmitted together using QPSK (quadrature phase-shift keying) modulation.

The ability to use different formats for communicating acknowledgment information allows for greater flexibility in performing ACK/NAK repetition, while avoiding or reducing the likelihood of ACK/NAK collisions.

FIG. 3 shows another example in which the ACK/NAK repetition is set at 3 (in other words three instances of ACK/NAK is sent by the mobile station in response to downlink data in a particular PDSCH subframe). When the ACK/NAK repetition is set at 3, data for the same mobile station cannot be sent in the downlink direction in more than two consecutive PDSCH subframes. Data for the same mobile station can be sent in two consecutive PDSCH subframes, followed by an intermediate subframe period that does not contain downlink data for the mobile station, then followed by another PDSCH subframe that contains data for the same mobile station. In the example of FIG. 3, data_1, data_2, and data_3 are sent in three different PDSCH subframes to the same mobile station. Data _1 is sent in PDSCH subframe n data_2 is sent in PDSCH subframe n+1, and data_3 is sent in PDSCH subframe n+3, where intermediate subframe n+2 (which does not contain downlink data for the mobile station) is provided to separate the transmission of data_2 and data_3. Downlink data can be scheduled to the same mobile station every two consecutive PDSCH subframes. However, after the two consecutive subframes, a separation subframe has to be provided before another PDSCH subframe can be sent to the same mobile station.

As further shown in FIG. 3, ACK/NAK_1 for data_1 is sent as three repeated instances in consecutive PUCCH subframes n+4, n+5, and n+6. The three repeated instances of ACK/NAK_2 (responsive to data_2) are sent in PUCCH subframes n+5, n+6, and n+7. Note that PUCCH in subframe n+5 and n+6 each contains both ACK/NAK_1 and ACK/NAK_2. No data for the mobile station is sent in PDSCH subframe n+2, since doing so would require an ACK/NAK in PUCCH subframe n+6 which already is sending two other ACK/NAK bits. Thus, a separation PDSCH subframe is provided between data_2 and data_3, such that ACK/NAK_3 starts in PUCCH subframe n+7 rather than PUCCH subframe n+6.

FIG. 4 is a flow diagram of a process according to an embodiment that is performed at the mobile station 110, which is assumed to be configured to perform ACK/NAK repetition. First downlink data is received (at 402) in a downlink channel subframe, such as a PDSCH subframe. Second downlink data is received (at 404) in another PDSCH subframe, which can be consecutive to the PDSCH subframe containing the first downlink data. In response to the first and second downlink data, the mobile station prepares (at 406) the repeated instances of acknowledgment information responsive to the first and second downlink data. It is assumed that the mobile station is configured to send two repeated instances in response to each piece of downlink data.

The mobile station sends (at 408) the two repeated instances of acknowledgment information responsive to the first downlink data in first and second consecutive uplink control channel (e.g., PUCCH) subframes. The first uplink control channel is at some offset from the downlink subframe carrying the first downlink data. The mobile station sends repeated instances of the acknowledgment information responsive to the second downlink data in second and third consecutive uplink control channel subframes (at 410).

Although reference is made to the mobile station performing the process of FIG. 4, it is noted that the base station can also be configured to perform the process of FIG. 4, where the base station is to acknowledge receipt of uplink information data (and/or signaling) from a mobile station.

In an alternative embodiment, it is contemplated that the mobile station can use a scheduled PUSCH (physical uplink shared channel) to send a repeated instance of ACK/NAK. Thus, for example, referring back to FIG. 2, if a PUSCH is scheduled to be sent in subframe n+5, then the ACK/NAK_1 that was supposed to have been sent in PUCCH subframe n+5 can instead be sent in PUSCH subframe n+5. The second repeated ACK/NAK_1 instance can be multiplexed with data on the PUSCH, according to the LTE standard.

As yet another alternative, if a PUSCH transmission was scheduled for subframe n+5, this PUSCH transmission can be skipped to avoid collision with the ACK/NAK scheduled to be sent in PUCCH subframe n+5.

The ACK/NAK repetition of a given mobile station is configurable by the base station. For example, the base station can send a parameter to the mobile station to specify the number of repetitions (2, 3, 4, or more). The mobile station-specific ACK/NAK repetition parameter can be configured by using RRC (radio resource control) signaling or other type of control signaling.

Instructions of software described above (including software 126 and 130 of FIG. 1) are loaded for execution on a processor (such as one or more CPUs 122 and 130 in FIG. 1). The processor includes microprocessors, microcontrollers, processor modules or subsystems (including one or more microprocessors or microcontrollers), or other control or computing devices. As used here, a “processor” can refer to a single component or to plural components (e.g., one CPU or multiple CPUs).

Data and instructions (of the software) are stored in respective storage devices, which are implemented as one or more computer-readable or computer- usable storage media. The storage media include different forms of memory including semiconductor memory devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable and programmable read-only memories (EPROMs), electrically erasable and programmable read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy and removable disks; other magnetic media including tape; and optical media such as compact disks (CDs) or digital video disks (DVDs). Note that the instructions of the software discussed above can be provided on one computer-readable or computer-usable storage medium, or alternatively, can be provided on multiple computer-readable or computer-usable storage media distributed in a large system having possibly plural nodes. Such computer-readable or computer-usable storage medium or media is (are) considered to be part of an article (or article of manufacture). An article or article of manufacture can refer to any manufactured single component or multiple components.

In the foregoing description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details. While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention. 

1. A method of providing acknowledgment information by a first wireless device, comprising: in response to receipt of first information from a second wireless device, preparing, by the first wireless device, to send repeated instances of acknowledgment information for the first information; sending, by the first wireless device, a first of the repeated instances of the acknowledgment information in a first frame structure, and a second of the repeated instances in a second, successive frame structure; and sending, by the first wireless device, further acknowledgment information in the second frame structure, wherein the further acknowledgment information is responsive to second information received from the second wireless device.
 2. The method of claim 1, wherein sending the repeated instances of the acknowledgment information in the respective first and second frame structures comprises sending the repeated instances of the acknowledgment information in respective first and second Evolved Universal Terrestrial Radio Access (EUTRA) subframes.
 3. The method of claim 2, wherein sending the second instance of the acknowledgment information comprises using a first information bit of the second subframe, and wherein sending the further acknowledgment information comprises using a second information bit of the second subframe.
 4. The method of claim 3, wherein using the first and second bits comprises using first and second ACK/NAK bits.
 5. The method of claim 4, further comprising modulating the first and second ACK/NAK bits in an uplink control channel subframe.
 6. The method of claim 4, wherein using the first and second ACK/NAK bits comprises using the first and second ACK/NAK bits of uplink control information in a physical uplink control channel (PUCCH) subframe.
 7. The method of claim 1, wherein sending the repeated instances of the acknowledgment information in the respective first and second frame structures comprises sending the repeated instances of the acknowledgment information in the respective first and second frame structures of a control channel, wherein the first instance of the acknowledgment information is sent according to a first format of the control channel, and the second instance of the acknowledgment information is sent according to a second, different format of the control channel.
 8. The method of claim 7, wherein the control channel is a physical uplink control channel (PUCCH).
 9. The method of claim 1, further comprising receiving the first information in a physical downlink traffic channel.
 10. The method of claim 1, further comprising: receiving third information from the second wireless device; sending, by the first wireless device, the first of repeated instances of acknowledgment information for the third information in a third frame structure, and a second of the repeated instances of the acknowledgment information for the third information in a fourth frame structure, wherein the first instance of the acknowledgment information for the third information is sent in a control channel, and the second instance of the acknowledgment information for the third information is sent in a traffic channel.
 11. The method of claim 10, wherein the control channel is a physical uplink control channel (PUCCH), and the traffic channel is a physical uplink shared channel (PUSCH).
 12. The method of claim 1, wherein an uplink traffic channel is scheduled to be communicated in a time interval for the second frame structure, the method further comprising deciding to not transmit the uplink traffic channel so that the second frame structure carrying the second repeated instance in an uplink control channel is sent.
 13. The method of claim 1, further comprising: receiving, by the first wireless device, a parameter set by the second wireless device to configure a number of repeated instances of acknowledgment information to send by the first wireless device in response to information received from the second wireless device.
 14. A first wireless device comprising: an interface to communicate wirelessly to a second wireless device; and a processor configured to: in response to receipt of first information from the second wireless device, prepare to send repeated instances of acknowledgment information for the first information; send a first of the repeated instances of the acknowledgment information in a first frame structure, and a second of the repeated instances in a second, successive frame structure; and send further acknowledgment information in the second frame structure, wherein the further acknowledgment information is responsive to second information received from the first wireless device.
 15. The first wireless device of claim 14, comprising a mobile station.
 16. The first wireless device of claim 14, comprising a base station.
 17. The first wireless device of claim 14, wherein the processor is configured to further receive a parameter configuring a number of the repeated instances of acknowledgment information, and wherein preparing to send the repeated instances of the acknowledgment information is according to the received parameter.
 18. The first wireless device of claim 17, wherein the received parameter specifies that the number is three or greater, and wherein the processor is configured to further send a third of the repeated instances in a third frame structure.
 19. The first wireless device of claim 18, wherein receiving the first and second information comprises receiving the first and second information in respective first and second traffic frame structures that are separated by at least one frame structure.
 20. An article comprising at least one computer-readable storage medium containing instructions that upon execution by a first wireless device cause the first wireless device to: receive first information from a second wireless device; send repeated instances of acknowledgment information for the first information, wherein the repeated instances of the acknowledgment information are sent in consecutive frame structures to the second wireless device; receive second information from the second wireless device; and send further acknowledgment information for the second information, wherein the further acknowledgment information is included in one of the frame structures carrying one of the repeated instances of the acknowledgment information for the first information.
 21. The article of claim 20, wherein the frame structures are Evolved Universal Terrestrial Radio Access (EUTRA) subframes. 